This invention relates in general to the field of thermoplastics and deals more particularly with the forming of thermoplastic laminates into various shapes.
Because thermoplastic laminates have many desirable qualities, they are widely used in a variety of applications. However, a major drawback associated with thermoplastic laminates is the considerable difficulty that is encountered in forming the laminates into the shapes that are necessary for them to function as major structural members. The most desirable laminates are obtained by consolidating multiple plies into flat sheets which harden when cooled to room temperature from the elevated consolidation temperature. Subsequent curving or bending of the laminate requires that the plies slip relative to one another, and this can be achieved only if the laminate is heated to the softening temperature at which ply slippage can occur.
In the past, techniques common in the metal bending technology have been used with thermoplastic laminates, despite the recognized differences in the properties of thermoplastic as compared to metal. For example, the entire laminate and sometimes the bending tool are heated to the softening temperature of the thermoplastic to allow ply slippage anywhere in the laminate at the same time. As can easily be appreciated, this technique requires a considerable amount of heat because it relies on heating of the entire laminate to the softening temperature. Due to the high cost of energy, the excessive heat that is required to carry out this process makes its practicality marginal at best. In addition, the tooling that is required is unduly complex, and the costs are increased accordingly.